Ten years on, the rising Swan will be one of the 46 men to take the field on Friday night at the MCG.
Unlike others when the Swans take on the Blues, the recently named All-Australian will go head-to-head with a club he not only supported growing up but idolised, which adds a surprising twist to the do-or-die qualifying final.
"I was a massive Carlton fan myself. I was actually talking to a few of the boys this week, and the last time Carlton played a final was in 2013 at the Accor (Stadium), and I cried the entire train ride home when the Swans beat the Blues by about seven goals," Gulden said.
"I chose Carlton which probably cost me a couple of premierships as a fan.
"They haven't played finals in a while, and they're probably one of the sleeping giants of the AFL, so it's great for the game to see them back playing in finals.
"The MCG is going to be packed and, personally, I cannot wait.”
Gulden has kicked 20 goals and averaged 27 disposals (19.3 kicks and 7.7 handballs), ten contested possessions, four total clearances and five marks per game. He will also head into the finals in prime form, having had a personal best haul of 42 touches against the Melbourne Demons in the Swans' final regular home and away game of the season.
After being awarded his first All-Australian selection and Casey Bunton Medal, the youngster will be looking to defeat his boyhood club in style.
As Gulden tries to guide the Swans to a back-to-back Grand Final appearance, two of his teammates - Chad Warner and Braeden Campbell - spoke on the midfielder's value on the field, his All-Australian season, and reminisced of stories they had of him since he joined the club three seasons ago.
"Obviously, myself and all the boys were so proud and obviously to do it in his third year, I guess something that not many people achieve, and I think this is just the start of what he can do, and hopefully we can see him perform in the finals as well," Warner said of Gulden's breakout year.
"I guess the main stories we have (are) on the golf course. He usually beats me a couple of times, but I beat him on the weekend, so I was pretty happy with that.
"We always argue and bicker on the golf course about who's better, and I think his handicap is a tiny bit lower than mine at the moment, which is a bit annoying."
Campbell, a fellow Swans Academy graduate, reflected on the journey Gulden has taken from the pair's days of junior football to now helping lead the Swans through September.
"Errol's been awesome since he's come in," Campbell said.
"(He's) come in on day one at the club and...I'm proud of him, and all the boys are proud of him, and it's just the effort that he's put in (and) he's got the rewards he's after.
"As a junior playing against Errol, it was always a massive game for me and also him. We played with each other in the New South Wales team, All-Australian team, then played against each other in the NAB All-Stars game, so it's been awesome, and I don't think we've actually pictured playing finals.
"He's all class of the field and pretty funny. He's just an awesome bloke to have around the club, and he's always up for a chat, and he's my closest mate."